title: A prototype hyperspectral system with a tunable laser source for retinal vessel imaging.
abstract: OBJECTIVE
  To describe the technology and determine the within-session repeatability of manual retinal reflectance measurements of arterioles and venules using a prototype hyperspectral retinal camera.
  
  
  METHODS
  Six healthy young volunteers (three males, average age 26 ± 4 years) had five repeated sets of retinal images captured between 500 and 600 nm at 5-nm intervals using a newly developed hyperspectral retinal camera. Optical densities were manually extracted for first-degree arterioles and venules and the repeatability of retinal reflectance was compared sequentially. The SDs of the differences between sequential mean values were used as an indication of the variance, while the coefficient of repeatability (COR) and intraclass correlation coefficient (ICC) were used to assess repeatability.
  
  
  RESULTS
  The mean difference between each sequential measure was calculated using 21 images from each of the five spectral cubes. The SDs of these values ranged from 0.01 to 0.06 OD units and from 0.01 to 0.07 OD units for first-degree arterioles and venules, respectively. The COR ranged from 0.02 to 0.11 OD units (relative to a mean OD of 0.15 [0.06-0.23] OD units) for arterioles and 0.03 to 0.14 OD units (relative to a mean OD of 0.25 [0.17-0.31] OD units) for venules. Good reliability (P < 0.001) was found for arterioles (ICC: 78.8%-94.4% with a Cronbach's α of 89.6%-97.6%) and for venules (ICC: 63.7%-92.1% with a Cronbach's α of 86.2%-98.1%).
  
  
  CONCLUSIONS
  Manual optical density determination with this novel hyperspectral camera showed very good intrasession (and intraobserver) repeatability with a small degree of variance that should form the basis of reliable retinal oxygen saturation values in future imaging research studies. Future automation of retinal vessel reflectance image analyses will likely further improve this repeatability.
authors.affiliation: Department of Ophthalmology and Vision Sciences, University Health Network, Toronto Western Hospital, Toronto, Canada. sunni_patel@hotmail.com
authors.forename: Sunni R
authors.initials: SR
authors.lastname: Patel
authors.forename: John G
authors.initials: JG
authors.lastname: Flanagan
authors.forename: Ayda M
authors.initials: AM
authors.lastname: Shahidi
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Sylvestre
authors.forename: Chris
authors.initials: C
authors.lastname: Hudson
mesh_terms: D000328:Adult; D001160:Arterioles / Q000166:cytology*; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007834:Lasers; D008297:Male; D012016:Reference Values; D015203:Reproducibility of Results; D012171:Retinal Vessels / Q000166:cytology*; D014699:Venules / Q000166:cytology*; D055815:Young Adult
keywords: hyperspectral imaging; repeatability; retinal imaging